She said she also saw Frank Felix, 25, and Joshua Acosta, 21 - who have been arrested for investigation of the murders - at furry events, and had met Felix at the Yost family home.
Two men and one teenage girl have been arrested in connection with the slaying of two men and one woman in Fullerton.
Fullerton Police officers on Sunday arrested Josh Acosta, 21 and Frank Felix, 25.
Katlynn Goodwill Yost, 17 was found unharmed on Sunday after the bodies of three people - Christopher Yos, 34, his wife, Jennifer Goodwill Yost, 39, and their friend, Arthur William Boucher, 28 - were found in Katlynn's Fullerton home.
The suspects are believed to have known the victims, Radus said.
"It is our hope these arrests will bring some comfort to the community and bring some peace to the families that were affected by this absolutely unthinkable crime".
At about 8:20 a.m. Saturday, police dispatchers received a call from a young girl who said that her parents died, Fullerton police Sgt. Jon Radus said in a statement.
Missing from the home was the victims' third child, 17-year-old Katlynn Goodwill Yost.
Radus, the police spokesman, said there were obvious signs of trauma to the bodies, but he would not release any details on how the adults might have died.
"He was always standing up for women in his family, me included", his girlfriend Joyce Burchett said through tears.
A report via abc7 notes Katlynn is the biological daughter of Jennifer Yost and stepdaughter of Christopher Yost. "That said, a 17 year old female juvenile has also been detained in connection with the murders and is in the custody of the Orange County Juvenile Hall", he added.
Shortly after the bodies were discovered, detectives learned that Katlynn was missing from the family home.
An alert was made to help locate Katlynn who was come Sunday, found safe and sound. "They're now without parents", Donna Trice told the newspaper.
Police are searching for a missing 17-year-old after three people were found dead inside a Fullerton home.
Formal charges will be announced and presented to the district attorney on Monday, Radus said.
Boucher, who went by Billy, had a 5-year-old son and was widely loved, Gracier said.